The BBC's Michael Buchanan in Washington says the court heard that prison guards were allowed to use a range of techniques, including cold showers, sleep deprivation and the aggressive use of military dogs to soften up prisoners for questioning.

But, he says Spc Graner's lawyers' case that he was merely following orders was seriously undermined when some of their own defence witnesses testified that he was not a law abiding soldier, and that many of the methods he is accused of using were not ordered by superiors.

Master Sgt Brian Lipinski, a commanding officer who served at the prison alongside Spc Graner, said Spc Graner disobeyed orders and lied about injuries.

'Lied about injuries'

Sgt Lipinski said Spc Graner wore his hair and uniform in violation of regulations and refused to stay away from Pte Lynndie England, who is also awaiting trial on abuse charges.

He also testified that Spc Graner lied about how a prisoner was injured.

The sergeant said Spc Graner had initially told him the inmate had injured his face and neck by tripping over some rubble in November 2003, but later admitted he had pushed the prisoner against a wall.

Another defence witness, intelligence officer Roger Brokaw, said physical and psychological techniques were used on prisoners to glean information amid pressure from superiors.

However, Mr Brokaw said he believed Spc Graner and others acted on their own accord.

"They assumed all Iraqis were terrorists and needed discipline," he told the court.

If convicted on all counts, Spc Graner faces up to 17-and-a-half years in prison.